荷电高聚物纳滤膜

本文对荷电聚合物纳纳滤膜的制备、性能及应用进行了全面的介和评述，反映了近年来荷电聚合笺纳滤膜研究的最新进展和动向。     

纳滤膜新型材料研究

纳滤是一种介于超滤与反渗透之间的重要膜分离过程,具有工作压力低、无相转变及分离效率高等独特优势。膜污染及渗透性/选择性之间的平衡是纳滤膜在使用和研发过程中面临的亟待解决的两个主要问题。膜材料是膜与膜分离技术的核心,开发新型的纳滤膜材料是解决上述问题的重要手段。本文从新型纳滤膜材料的设计与选择的角度出发,总结归纳了近年来新型材料在纳滤膜的制备与应用研究现状,包括新型有机纳滤膜材料、新型无机纳滤膜材料和新型有机-无机杂化纳滤膜材料三个方面,拓展了对纳滤膜材料的认知,探讨了新型纳滤膜材料的共性及其存在的主要问题,并对未来高性能纳滤膜材料的研制方向进行了展望。     

纳滤膜在水处理中的最新应用进展

纳滤膜(NF)是新的分离膜品种,对溶质的截留性能介于超滤膜(UF)和反渗透膜(RO)之间。纳滤膜的特性是表面带有电荷并具有纳米级的微孔,能够去除高价离子和分子量大于200的溶解性的有机物。特殊的分离效果使纳滤技术单独或者和其它技术联用应用于水处理领域,主要包括:(1)饮用水制备和深度净化;(2)海水淡化;(3)废水处理,例如生活污水、垃圾渗滤液等等。本文综述了纳滤技术在上述水处理领域中的应用进展及现存问题。     

聚电解质层层自组装纳滤膜*

层层自组装技术能够方便地对膜的微观结构和组成进行调控,已在制备复合型纳滤膜方面取得了迅速的发展。本文综述了近年来用于聚电解质层层自组装纳滤膜的制备方法,种类以及影响因素。介绍了静态层层交替沉积、压力驱动自组装和电场强化自组装等三种制备方法;归纳了均聚型、共聚型和有机/无机杂化型等三类用于层层自组装纳滤膜的聚电解质的特点;讨论了聚电解质的荷电性、电荷密度和电离程度等因素对其自组装膜分离性能的影响。总结了聚电解质自组装纳滤膜在水处理和有机溶剂中物质的分离等方面的应用。同时,对提高聚电解质自组装纳滤膜的组装效率,分离性能和发展方向提出了设想和建议。     

聚酰胺纳滤膜对黄连中生物碱的截留性能

以盐酸小檗碱为模型分子,考察循环时间、操作压力、料液浓度和离子强度等因素对聚酰胺纳滤膜截留盐酸小檗碱性能的影响。实验表明:聚酰胺纳滤膜对盐酸小檗碱的截留率80min后基本稳定;随着操作压力的增加,膜通量和截留率都增大;随着料液浓度的增加,聚酰胺纳滤膜通量下降,对盐酸小檗碱的截留率先增大后下降;随着溶液中离子强度的增加,膜通量和截留率都减小。在黄连提取液中生物碱含量为0.025g/L、操作压力为0.4MPa条件下,聚酰胺纳滤膜5min可使黄连提取液中生物碱浓缩6.27倍。     

盐湖提锂纳滤膜研究进展

锂是我国发展新能源等产业的关键资源,进口依赖度大。盐湖提锂是应对锂短缺问题的重要途径,然而盐湖中高浓度的伴生镁离子给高效提锂带来挑战。纳滤膜可通过孔径筛分和电荷排斥效应的协同,有效分离镁锂离子,在盐湖提锂中扮演着重要的角色。本文从纳滤膜结构(孔径、电荷、厚度)调控出发,介绍了新单体设计、表面改性、共混掺杂、底膜改性等膜结构调控策略,阐述了膜结构与镁锂分离性能的构效关系,总结了不同制膜方法在镁锂分离过程中的优劣,展望了新型镁锂分离纳滤膜的研究方向。     

氮气等离子体改性壳聚糖-聚丙烯腈复合纳滤膜

以氮气低温等离子体对壳聚糖-聚丙烯腈复合纳滤膜进行表面改性。用接触角、扫描电镜、扫描探针显微镜、X射线光电子能谱观察膜表面的亲水性和形貌特征,分析膜表面化学组成;以γ-氨基丁酸为分离对象表征膜的纳滤性能。结果表明:经50 W、20 Pa的氮气等离子体作用2 min,壳聚糖膜表面的亲水性大幅改善,其接触角由102.0°下降至44.3°,平整度明显提升;膜表面中的C—C、C—O和酰胺基团均减少,而胺基和羰基相应增加;在pH=6.15的水溶液中对w=1.0%的γ-氨基丁酸进行纳滤,液体通量由原来的1.12 L/(m~2·h)提高至1.75 L/(m~2·h),且对氨基酸的截留率从28%提升至83%。     

静电位阻模型在纳滤膜跨膜电位解析中的应用

采用静电位阻模型对纳滤膜的跨膜电位进行了理论解析, 考察了溶液体积通量密度、原料液浓度、阴阳离子扩散系数比、膜孔半径和膜体积电荷密度对KCl(1-1型电解质)和MgCl2(2-1型电解质)中的纳滤膜跨膜电位的影响. 研究结果表明, 随着通量密度的增大, KCl和MgCl₂的跨膜电位线性程度增强; 两种电解质的跨膜电位均随着原料液浓度和膜孔半径的增大而下降; 在不同的考察范围内, 阴阳离子扩散系数比对1-1型和2-1型电解质的跨膜电位的影响差别较大; KCl的跨膜电位随着膜体积电荷密度的变化关于零点呈现出对称性, 而MgCl₂的跨膜电位零点则出现在膜体积电荷密度为负的条件下.     

二胺结构对聚酰胺复合纳滤膜性能的影响

分别以邻苯二胺、间苯二胺、对苯二胺为水相单体,均苯三甲酰氯(TMC)为油相单体,聚醚砜超滤膜为基膜,界面聚合法制备了复合纳滤膜.在纳滤膜对Na<,2>SO<,4>,MgSO<,4>,MgCl<,2>和NaCl四种盐的脱盐率中,间苯二胺膜最高,对苯二胺膜居中,邻苯二胺膜最差;在纳滤膜耐氯性能方面,对苯二胺最佳,邻苯二胺居...     

界面聚合法制备聚哌嗪酰胺复合纳滤膜

以聚醚砜超滤膜为基膜,哌嗪(PIP)为水相单体,均苯三甲酰氯(TMC)为有机相单体,采用界面聚合法制备了复合纳滤膜,扫描电镜、表层的红外分析结果表明在基膜表面聚合了一层聚酰胺膜,膜性能测定结果表明膜表面荷负电,对不同无机盐的截留率为Na2SO4MgSO4MgCl2NaCl。界面聚合条件对膜性能的影响表明,最佳聚合条件为:PIP浓度0.5%～2%,TMC浓度0.15wt%～0.75wt%,聚合时间≥1min,热处理温度60℃～80℃,时间15 min左右。     

聚二苯基乙炔耐溶剂纳滤膜的制备与性能

聚二苯基乙炔(PDPA)不溶于有机溶剂,是理想的新型耐溶剂纳滤膜材料。采用溶液浇铸法制备聚[1-(4-三甲基硅基)苯基-2-苯乙炔](PTMSDPA)均质膜,经脱硅反应得到PDPA膜,研究其乙醇渗透性能和染料截留性能。结果表明,乙醇渗透通量与压力呈正相关性,传质机理可能介于孔流机理和溶解扩散机理之间的过渡区。染料的分子尺寸、电荷性质以及染料和膜之间的相互作用共同影响PDPA膜的截留性能。     

Electroviscous Effects in Ceramic Nanofiltration Membranes

Membrane permeability and salt rejection of a γ‐alumina nanofiltration membrane were studied and modeled for different salt solutions. Salt rejection was predicted by using the Donnan‐steric pore model, in which the extended Nernst–Planck equation was applied to predict ion transport through the pores. The solvent flux was modeled by using the Hagen–Poiseuille equation by introducing electroviscosity instead of bulk viscosity. γ‐Alumina particles were used for ζ‐potential measurements. The ζ‐potential measurements show that monovalent ions did not adsorb on the γ‐alumina surface, whereas divalent ions were highly adsorbed. Thus, for divalent ions, the model was modified, owing to pore shrinkage caused by ion adsorption. The ζ‐potential lowered the membrane permeability, especially for membranes with a pore radius lower than 3 nm, a ζ‐potential higher than 20 mV, and an ionic strength lower than 0.01 m . The rejection model showed that, for a pore radius lower than 3 nm and for solutions with ionic strengths lower than 0.01 m , there is an optimum ζ‐potential for rejection, because of the concurrent effects of electromigration and convection. Hence, the model can be used as a prediction tool to optimize membrane perm‐selectivity by designing a specific pore size and surface charge for application at specific ionic strengths and pH levels.     

Crosslinked Polyvinylnorbornene‐Based Membranes as a New Class of Solvent‐Resistant Nanofiltration Membranes

Solvent resistant nanofiltration (SRNF) has received increasing attention since the turn of the century within energy‐ and waste‐efficient unit processes. This work explores the synthesis and characterization of crosslinked polynorbornenes for SRNF. A series of polyvinylnorbornene thin‐film composite membranes with increasing degree of crosslinking were prepared and tested for their SRNF performance in heptane, chloroform, and toluene. Sudan Black B (457 g mol^?1) was used as the solute. Then, 99% retention was achieved in heptane, 86% in chloroform, and 75% in toluene. It was further shown that the permeance and retention can be fine‐tuned in these solvents by controlling the extent of crosslinking. This work thus introduces the crosslinking of polynorbornenes as a promising material route for SRNF. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1593–1600     

Ultra-Fast Preparation of Large-Area Graphdiyne-Based Membranes via Alkynylated Surface-Modification for Nanofiltration

Graphdiynes (GDYs), two-dimensional graphene-like carbon systems, are considered as potential advanced membrane material due to their unique physicochemical features. Nevertheless, the scale-up of integrated GDY membranes is technologically challenging, and most studies remain at the theoretical stage. Herein, we report a simple and efficient alkynylated surface-mediated strategy to prepare hydrogen-substituted graphdiyne (HsGDY) membranes on commercial alumina tubes. Surface alkynylation initiates an accelerated surface-confined coupling reaction in the presence of a copper catalyst and facilitates the nanoscale epitaxial lateral growth of HsGDY. A continuous and ultra-thin HsGDY membrane (∼100 nm) can be produced within 15 min. The resulting membranes exhibit outstanding molecular sieving together with excellent water permeances (ca. 1100 L m⁻² h⁻¹ MPa⁻¹), and show a long-term durability in cross-flow nanofiltration, owing to the superhydrophilic surface and hydrophobic pore walls.     

荷正电聚乙烯亚胺纳滤膜的制备与应用

纳滤是介于超滤与反渗透之间的膜分离技术,具有操作压力低,无相变,分离效率高及运行成本低等优点,广泛地应用于饮用水制备、污水处理、化工、制药和食品等领域.近年来,随着分离体系复杂程度的增加及对膜分离性能要求的提高,荷正电纳滤膜越来越受到研究者的关注.聚乙烯亚胺(PEI)是一类重要的多胺类荷正电纳滤膜材料,具有优异的亲水性、高荷电密度及反应活性.开发具有高分离性、高稳定性、耐酸碱性、耐溶剂性、抗菌性和耐污染性的荷正电PEI纳滤膜(P-PEI-NFM)日益成为研究的热点.本文对近年来P-PEI-NFM的制备方法进行归纳,总结了P-PEI-NFM在水软化、重金属脱除、碱性染料的分离及浓缩、抗生素分离和耐溶剂纳滤的应用.探讨了P-PEI-NFM存在的主要问题,并对未来的研究方向进行了展望.     

Self‐Assembled Asymmetric Block Copolymer Membranes: Bridging the Gap from Ultra‐ to Nanofiltration

The self‐assembly of block copolymers is an emerging strategy to produce isoporous ultrafiltration membranes. However, thus far, it has not been possible to bridge the gap from ultra‐ to nanofiltration and decrease the pore size of self‐assembled block copolymer membranes to below 5 nm without post‐treatment. It is now reported that the self‐assembly of blends of two chemically interacting copolymers can lead to highly porous membranes with pore diameters as small as 1.5 nm. The membrane containing an ultraporous, 60 nm thin separation layer can fully reject solutes with molecular weights of 600 g mol^?1 in aqueous solutions with a water flux that is more than one order of magnitude higher than the permeance of commercial nanofiltration membranes. Simulations of the membrane formation process by dissipative particle dynamics (DPD) were used to explain the dramatic observed pore size reduction combined with an increase in water flux.     

Solvent‐Resistant Nanofiltration for Product Purification and Catalyst Recovery in Click Chemistry Reactions

The quickly developing field of “click” chemistry would undoubtedly benefit from the availability of an easy and efficient technology for product purification to reduce the potential health risks associated with the presence of copper in the final product. Therefore, solvent‐resistant nanofiltration (SRNF) membranes have been developed to selectively separate “clicked” polymers from the copper catalyst and solvent. By using these solvent‐stable cross‐linked polyimide membranes in diafiltration, up to 98 % of the initially present copper could be removed through the membrane together with the DMF solvent, the polymer product being almost completely retained. This paper also presents the first SRNF application in which the catalyst permeates through the membrane and the reaction product is retained.     

Recovery of Anthocyanins and Monosaccharides from Grape Marc Extract by Nanofiltration Membranes

Wastewaters and by-products generated in the winemaking process are important and inexpensive sources of value-added compounds that can be potentially reused for the development of new products of commercial interest (i.e., functional foods). This research was undertaken in order to evaluate the potential of nanofiltration (NF) membranes in the recovery of anthocyanins and monosaccharides from a clarified Carménère grape marc obtained through a combination of ultrasound-assisted extraction and microfiltration. Three different flat-sheet nanofiltration (NF) membranes, covering the range of molecular weight cut-off (MWCO) from 150 to 800 Da, were evaluated for their productivity as well as for their rejection towards anthocyanins (malvidin-3-O-glucoside, malvidin 3-(acetyl)-glucoside, and malvidin 3-(coumaroyl)-glucoside) and sugars (glucose and fructose) in selected operating conditions. The selected membranes showed differences in their performance in terms of permeate flux and rejection of target compounds. The NFX membrane, with the lowest MWCO (150–300 Da), showed a lower flux decay in comparison to the other investigated membranes. All the membranes showed rejection higher than 99.42% for the quantified anthocyanins. Regarding sugars rejection, the NFX membrane showed the highest rejection for glucose and fructose (100 and 92.60%, respectively), whereas the NFW membrane (MWCO 300–500 Da) was the one with the lowest rejection for these compounds (80.57 and 71.62%, respectively). As a general trend, the tested membranes did not show a preferential rejection of anthocyanins over sugars. Therefore, all tested membranes were suitable for concentration purposes.